Solar energy generation and storage system

ABSTRACT

A solar energy system including a plurality of solar panels mounted at an angle on a flotation device floating on a body of water is provided. A mechanism rotates the flotation device to substantially track the sun as it traverses the sky. The rotation of the flotation device and angled solar panels increases the proportion of incident sunlight that impacts the panels in an approximately perpendicular direction, allowing the sunlight to be absorbed by the panels and converted to electrical energy. The system also stores the energy collected during the day for later use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Patent Application No. 60/882,909, filed Dec. 30, 2006, the entire contents of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to energy systems, and more specifically to systems that convert and store solar energy.

BACKGROUND

Solar panels made up of a plurality of photovoltaic (PV) cells are often used for the direct conversion of sunlight to electrical energy. Such panels may be mounted on rooftops or other exterior structures exposed to the sun to provide electric power for use by or within the structure. In addition to receiving power from the panels, a structure may be connected to the local power grid to draw power from the grid at night or during overcast days and even to provide power to the grid when the amount of power created exceeds the energy usage of the structure.

The amount of sunlight that a solar panel absorbs, and therefore the amount of electrical energy it generates, varies greatly with its orientation relative to the sun. PV cells provide their maximum output when solar rays impact them in a direction that differs from the perpendicular or “normal” direction by no more than a preselected angle. When sunlight impinges on PV cells at an angle that differs appreciably from the preferred, normal direction, their output decreases. Therefore, solar panels may be mounted at an angle with respect to the horizon to increase the amount of sunlight that impacts them at angles close to the normal direction. In addition, systems have been proposed for moving solar panels over the course of a day to “track” the sun as it moves across the sky. Such systems can be made to closely approximate normal incidence on a continuous basis, but they are also rather complex and expensive to operate and maintain.

Thus, there is a need for a simple and effective system for increasing the proportion of incident sunlight that impacts at an angle sufficient for it to be absorbed by the panels and therefore converted to electrical energy. In addition, there is a need for solar energy systems that can efficiently and conveniently store the energy collected during daylight hours for later use.

SUMMARY OF THE INVENTION

The solar energy system of the present invention provides a simple and efficient mechanism for capturing, converting, and storing solar energy. The system includes a plurality of solar panels mounted at an angle on a flotation device floating on a body of water. A mechanism rotates the flotation device to substantially track the sun as it traverses the sky. The rotation of the flotation device and angled solar panels increases the proportion of incident sunlight that impacts the panels in an approximately perpendicular direction, allowing the sunlight to be absorbed by the panels and converted to electrical energy. The system may also store energy collected during the day for later use by pumping water to a higher elevation, where the solar energy is stored in the form of potential energy of the elevated water.

In an embodiment of the invention, a solar energy system includes a flotation device floating on a body of water; a plurality of solar panels supported on the flotation device, each of the solar panels being inclined in the same direction relative to the surface of the water; and a mechanism for rotating the flotation device on the body of water to substantially track the sun as it moves across the sky.

In another embodiment of the invention, the solar energy system includes first and second bodies of water, the second body of water being located at a higher elevation than the first body of water; at least one flotation device floating on at least one of the bodies of water; a plurality of solar panels mounted at an angle on the flotation device; a mechanism for rotating the flotation device to track the sun; a pump electrically coupled to the solar panels and configured to pump water from the first body of water to the second body of water; and a turbine positioned between the first and second bodies of water to extract energy from the water flowing from the second body of water to the first body of water.

In yet another embodiment of the invention, a solar energy system also includes a mechanism for adjusting the angle at which the solar panels are mounted on the flotation device. The system may also include a controller that controls rotation of the flotation devices to rotate them approximately 360° in 24 hours. The solar energy system may also include a connection to the external power grid.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be appreciated as the same become better understood with reference to the specification, claims, and appended drawings wherein:

FIG. 1 is a top plan view of a solar energy system constructed according to an embodiment of the present invention;

FIGS. 2 a and 2 b are side elevational views of the solar energy system of FIG. 1;

FIGS. 3 a, 3 b, and 3 c are schematic representations of solar energy systems constructed according to different embodiments of the invention;

FIG. 4 is a fragmentary top plan view of a solar energy system in another embodiment of the invention in the region of a central shaft about which solar modules of the invention rotate; and

FIG. 5 is a fragmentary vertical cross-sectional view of a solar energy system constructed according to a further embodiment of the invention.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the drawings is intended as a description of the presently preferred embodiments of a solar energy generation and storage system provided in accordance with the present invention and is not intended to represent the only forms in which the invention may be constructed or utilized. It is to be understood that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers indicate like elements or features.

FIG. 1 depicts a solar energy system 10 constructed according to an embodiment of the present invention. The system 10 includes a lower pond 12 and an upper pond 14 having respective central shafts 20 and 22. A circular array of solar panels 16 in the lower pond 12 surrounds the central shaft 20, and a similar array of solar panels 18 in the upper pond 14 surrounds the central shaft 22. The arrays 16 and 18 are each made up of a plurality of interfitting flotation devices 26 onto which individual solar panels 28 are mounted. The solar panels 28 are mounted at an angle relative to the horizon, as shown in FIGS. 2 b and 5 and described below.

During the day, the solar panels 28 absorb incoming sunlight and generate electricity. Motors 54 and 56, which engage the outer edges of the arrays 16 and 18, rotate the arrays about their central shafts 20 and 22. Although FIG. 1 shows one motor attached to each array, any convenient number of motors can be used. The motors rotate the arrays to orient the angled solar panels 28 toward the sun as it traverses the sky from east to west. The motors may be controlled to rotate the array 360°, one full rotation, every 24 hours. In addition, or alternatively, the motors may be controlled by a system that senses the sun's movement across the sky and either controls the speed of the motors or turns the motors on and off to track the sun. Periodic adjustments can be made to increase or reduce the rotational speed of the arrays to make corrections if the rotation deviates from a preselected schedule, or to account for seasonal changes in the sun's path across the sky. In most cases, the aggregate mass of each array of panels is quite large, making it desirable to maintain the rate of rotation as uniform as possible.

The solar panels 28 may be any available type of solar panel including substrate-based devices such as single crystalline or polycrystalline silicon devices, or thin film devices such as amorphous or microcrystalline silicon, or any of a variety of compound semiconductor devices. In one embodiment, the solar panels 28 are polycrystalline silicon devices of the type marketed by General Electric Company as model no. GEPVp-200.

The panels 28 are mounted on the flotation devices 26, which float on the surface of the ponds. The flotation devices 26 may be constructed of a suitable closed cell foam, such as Styrofoam™, or any other suitable foam or non-foam material, such as polystyrene or polyethylene materials or combinations. The devices may be coated with composite carbon or glass fiber reinforced material or any other suitable coating known in the art. The arrays 16 and 18, including all of the flotation devices 26 and solar panels 28, may be of any desired size, and in one embodiment weigh between 10,000 and 20,000 tons. In such a case, each pond 12 and 14 may occupy between 50 and 200 acres. The ponds 12 and 14 may be lined with a water-impermeable material to prevent water leaks. For example, the ponds may be lined with a water-tight earthen material such as clay, or with polyvinyl chloride (PVC), cement, or any other suitable water-tight material.

FIG. 2 a shows a side view of the solar energy system 10 in one embodiment of the present invention. In this embodiment, the upper pond 14 is located at a higher elevation than the lower pond 12. As the figure shows, the upper pond 14 is located at a distance D above the lower pond 12. Flotation devices 26 float on the surface of both ponds 12 and 14, and the solar panels 28 are mounted on the flotation devices 26. The two ponds are separated by a slope 42, which is preferably a 2:1 (horizontal:vertical) slope.

Two flow channels connect the ponds 12 and 14. A first flow channel 34 connects the lower pond 12 to the upper pond 14. A pump 30 located in the first flow channel 34 pumps water from the lower pond 12 to the upper pond 14. A second flow channel 36 connects the upper pond 14 to the lower pond 12. A turbine 32 is located in the second flow channel 36 to extract energy from water flowing from the upper pond 14 down to the lower pond 12.

During the day, sunlight shines on the solar panels 28, and the motors 54 and 56 rotate the solar panels to track the sun through the sky. The solar panels 28 generate electricity, which may be used to power the pump 30 to move water from the lower pond 12 to the upper pond 14. If the solar panels 28 generate more electricity than is needed to operate the pump 30, the surplus electricity can used otherwise or sold to the external power grid.

After the sun sets, at least some of the solar energy collected during the day by the solar panels 28 may remain stored in the form of potential energy of the elevated water in the upper pond 14. This potential energy can be captured and converted into electricity by allowing the elevated water in the upper pond 14 to drain through the second flow channel 36, across the turbine 32, and into the lower pond 12. The flowing water powers the turbine 32 to generate electricity. Thus, the solar energy system 10 enables solar energy to be collected during the day, stored as potential energy, and then used at any later time to satisfy a demand for electric power. After the elevated water powers the turbine 32 and returns to the lower pond 12, it can be pumped back to the upper pond 14 the next day, when the sun rises and shines on the solar panels 28.

The solar energy system 10 may also be connected to an external power grid (not shown) so that surplus energy generated by the solar panels 28 during the day can be sold to the power grid. The solar panels 28 may be connected to the external power grid through the central shafts 20 and 22. A slip ring fitted to the central shaft can maintain the electrical connection to the solar panels 28 as they rotate. The electricity generated by the turbine 32 when water is drained from the upper pond 14 to the lower pond 12 can also be sold to the external power grid, or it can be used locally. Additionally, at times when the external power grid has surplus energy, that energy can be used to drive the pump 30 to move water from the lower pond to the upper pond. The solar energy system can thus store excess energy from the power grid in the form of potential energy of the elevated water in the upper pond 14.

As the sun travels across the sky during a day, the motors 54 and 56 rotate the arrays 16 and 18 around the central shafts 20 and 22 in order to point the angled solar panels 28 generally toward the sun. This increases the amount of sunlight the solar panels 28 absorb and the amount of electricity they produce. The ponds 12 and 14 facilitate the rotation by providing a low-friction surface on which the arrays 16 and 18 can rotate. This low-friction surface reduces the amount of energy required to drive the motors 54 and 56 that rotate the arrays of solar panels. Once the motors overcome the inertia of the large arrays 16 and 18, the arrays rotate easily on the water. The low-friction water surface of the ponds thus contributes to the overall energy efficiency of the system.

A gap 24 separates the outer edge of the arrays 16 and 18 from the outer edges of the ponds 12 and 14. In a preferred embodiment, the gap may range from about 40 to about 60 feet in width. This gap provides a ring of exposed water surrounding the arrays 16 and 18. This exposed water deters animals from jumping or walking onto the arrays 16 and 18 and possibly damaging the flotation devices 26 and solar panels 28. The gap also eliminates friction or interference between the edge of the array and the edge of the pond as the array rotates.

FIG. 2 b is a side view of the solar panels 28 and the flotation devices 26 in an embodiment of the invention. The solar panels 28 are mounted at an angle on the flotation devices 26, with spaces 52 between the solar panels 28 to prevent adjoining panels from casting shadows on each other and thereby reducing the amount of sunlight absorbed. The spaces 52 also facilitate repair of the system 10 by providing room for repair or maintenance crews to walk between the panels 28. In the embodiment of FIG. 2 b, the spaces 52 can range from about 1 to about 3 feet in width.

FIGS. 3 a, 3 b, and 3 c are side views of the solar energy system 10 in three different embodiments. In these embodiments, the solar energy system 10 has an additional feature, in that it serves as a water storage station as well as an energy generation and storage system. In FIG. 3 a, both ponds 12 and 14 hold stored water in addition to the water that is pumped between them. At the top of FIG. 3 a, the upper pond 14 is full, holding both stored water and pumped water. The lower pond 12 is only half full, holding stored water but no additional water that can be pumped to the upper pond 14. All of the water available for pumping has been pumped to the upper pond 14 from the lower pond 12. The pumped water is ready to be drained back to the lower pond to power the turbine 32 to generate electricity. Once the pumped water has been drained, the solar energy system 10 will appear as shown in the bottom of FIG. 3 a. The lower pond 12 will be full, holding stored water and the drained water. The upper pond 14 will be half full, holding stored water but empty of all the water that was drained to the lower pond 12.

In FIG. 3 b, only the upper pond 14 holds stored water. At the top of FIG. 3 b, all of the pumped water is held by the upper pond 14, and the lower pond 12 is empty. When energy is needed, the pumped water is drained from the upper pond 14 down to the lower pond 12, as shown at the bottom of FIG. 3 b. At this point the lower pond 12 holds all of the drained water, and the upper pond 14 still holds all of the stored water.

A third embodiment is shown in FIG. 3 c. Neither pond holds any stored water, but both ponds are available for water storage. The pumped water occupies only half the capacity of either pond, so either or both ponds may have the rest of their capacity filled with stored water. At the top of FIG. 3 c, all of the pumped water is held by the upper pond 14 and the lower pond 12 is empty. When the lower pond is empty, the array of solar panels 16 floating on the lower pond 12 rests at the bottom of the pond, in the lower resting position 38 (shown in phantom lines FIG. 2 a). At the bottom of FIG. 3 c, the water has been drained back down to the lower pond 12. The upper pond 14 is then empty, and the array of solar panels 18 of the upper pond 14 rests at the bottom of the pond, in the lower resting position 40 (shown in FIG. 2 a).

In the embodiments of FIGS. 3 a, 3 b, and 3 c, the solar energy system 10 serves both as an energy generation and storage system and a backup water supply station. Either or both ponds may be built with a capacity larger than necessary for the solar energy system, so that the ponds can hold more water than is pumped between them. This additional stored water may provide a backup water supply during a water shortage, or may be used during a fire or drought or other emergency situations.

Referring now to FIG. 4, the central shaft 20 is circular in cross section and may have a cross-sectional diameter of about 40 to 70 feet. The shaft may have a steel or concrete exterior, and may be hollow or filled with sand, earth, concrete, or other suitable filler material. Panels 46 are attached to the flotation devices 26 closest to the central shaft 20 to fill in the space between the devices and the shaft. Bearings 48 are coupled to the outer surface of the central shaft 20 to facilitate rotation of the flotation devices about the shaft. The bearings reduce the friction between the panels 46 and the outer surface of the shaft 20 as the motor rotates the devices about the shaft. In other embodiments, other friction-reducing elements, such as rollers, wheels, or polymer blocks, may be used in place of or in addition to the bearings 48.

FIG. 4 also shows a triangular bracket 44 which may be used to connect adjoining flotation devices 26 to each other. In this embodiment, the flotation devices are hexagonal in shape, forming a three-pointed corner where three devices meet. A triangular bracket 44 is secured at these corners to attach the three adjoining devices to each other. The hexagonal devices are attached together at each corner to form an interlocking array of flotation devices. The devices fit tightly against each other to prevent algae growth between them. When the flotation devices are hexagonal, only three devices are attached at each corner, as opposed, for example, to square devices that form corners where four devices meet, or triangular devices that form corners where five or more devices meet. Thus, the use of hexagonal flotation devices reduces the number of devices that meet at each corner to three, improving the stability of the array.

In the embodiment shown in FIG. 4, four solar panels 28 are mounted on each flotation device 26, and each solar panel 28 spans two flotation devices. The solar panels 28 can be staggered such that one panel reaches across an intersection of two flotation devices while the next adjoining panel does not. This staggered arrangement reinforces the array, increasing its rigidity and stability and spreading out the load on the brackets 44.

FIG. 5 is a vertical cross-sectional view of solar energy panels 28 in an embodiment of the present invention. Each solar panel 28 is mounted on a frame 50 that is attached to the flotation device 26. The panel 28 may be glued, welded, bolted, or otherwise attached to the frame 50 in any suitable manner known in the art. The frame 50 may be constructed of metal, reinforced resin, or other suitable material, and the frame may be attached to the flotation device 26 by rivets, bolts, or other suitable fastening means (not shown). The frames 50 hold the panels 28 at an angle Θ with respect to the horizon. All of the panels 28 of the array may be inclined at the same angle Θ so that they are all pointed in the same direction, i.e., so that lines normal to the surface of the panels are parallel to one another.

The optimal angle of incline Θ depends on the latitude of the site where the solar energy system is located. At each latitude, an angle can be selected to provide the panels 28 with a large proportion of the available sunlight over the course of a day as the array of panels rotates. It will be understood, however, that no fixed angle can provide an optimal orientation at all times. Rather, the fixed arrangement disclosed herein is a compromise intended to approximate, as closely as possible, a normal angle of incidence over the course of a year. While the disclosed arrangement is less efficient in terms of solar energy conversion than a full two-axis tracking system, the advantage lies in the fact that the conversion efficiency is considerably higher than a stationary system with much less mechanical complexity and expense than a two-axis system.

In another embodiment, also shown in FIG. 5, the mounting structure 50 may include an actuator 60 for raising and lowering one end or side of the solar panels 28, thereby increasing or decreasing the angle Θ. Adjustments to the angle Θ can improve the efficiency of the system by increasing the amount of sunlight that impacts the panels 28 in a direction within a preselected angle of normal incidence. The actuator 60 can thus adjust the angle Θ during the course of a day and/or a year to more accurately track the sun's movement. The actuator 60 may be a screwjack or any other suitable lifting mechanism known in the art. While the actuator 60 adds a degree of additional complexity to the system, the system is still considerably easier to install and maintain than a full two-axis tracking system.

Also, because the solar panels 28 are angled, dirt and debris tends to roll or slide off, instead of accumulating on the panels. However, fine dust particles may still accumulate on the top surfaces of the panels 28, decreasing the efficiency of the panels by blocking incoming solar radiation. Therefore, the solar energy system 10 of the present invention may include a sprinkler system 70 (FIG. 5) to rinse away such dust and dirt. The sprinkler system 70 can include one or more sprinkler heads 72 and a pump (not shown) to draw water from the ponds below the arrays. The sprinkler system 70 can be cycled on a regular schedule, or may be used whenever needed. When in use, the pump draws water from the ponds, and the sprinkler heads spray the pumped water onto the top surfaces of the panels 28. The water will run down the angled panels, carrying dust and dirt away with it and re-exposing the panels to the sun. The sprinkler system 70 thus improves the overall efficiency of the solar panels 28.

FIG. 5 also shows the spacing 52 between the solar panels 28. This spacing prevents shadows from one panel from falling on an adjoining panel and thereby reducing the output of the system. It also facilitates repair, maintenance, and cleaning of the arrays.

Although limited embodiments of the solar energy system and its components have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. Accordingly, it is to be understood that the solar energy system and its components constructed according to principles of this invention may be embodied other than as specifically described herein. The invention is also defined in the following claims. 

1. A solar energy system comprising: a flotation device floating on a body of water; a plurality of solar panels supported on the flotation device, each of the solar panels being inclined relative to the surface of the water; and a mechanism for rotating the flotation device on the body of water to substantially track the sun as it moves across the sky.
 2. The solar energy system of claim 1, further comprising: a second body of water located at a higher elevation than the first body of water; a pump electrically coupled to the solar panels and configured to pump water from the first body of water to the second body of water; a turbine positioned between the two bodies of water to extract energy from water flowing from the second body of water to the first body of water.
 3. The solar energy system of claim 1, further comprising a mechanism for adjusting the direction in which the solar panels are inclined.
 4. The solar energy system of claim 1, further comprising a controller that controls the mechanism for rotating the flotation device.
 5. The solar energy system of claim 4, wherein the controller comprises a sensor that senses the position of the sun.
 6. The solar energy system of claim 1, wherein the solar panels are electrically coupled to an external power grid.
 7. The solar energy system of claim 1, wherein the solar panels are selected from the group consisting of single crystalline devices, polycrystalline silicon devices, amorphous silicon devices, microcrystalline silicon devices, and compound semiconductor devices.
 8. The solar energy system of claim 1, wherein the flotation device comprises a plurality of flotation segments connected together.
 9. The solar energy system of claim 8, wherein the flotation segments are hexagonal.
 10. The solar energy system of claim 9, wherein the flotation segments are connected together by triangular brackets.
 11. A solar energy system comprising: a shaft disposed within a body of water; a plurality of flotation devices floating on the body of water and connected together to surround the shaft; a plurality of solar panels mounted on the flotation devices at an angle relative to the horizon; and a motor attached to at least one of the flotation devices to rotate the flotation devices about the shaft.
 12. The solar energy system of claim 11, further comprising: a second body of water at a higher elevation than the first body of water; first and second channels connecting the first body of water to the second body of water; a pump electrically coupled to the solar panels and positioned in the first channel to pump water from the first body of water to the second body of water; a turbine positioned in the second channel to extract energy from water flowing from the second body of water to the first body of water.
 13. The solar energy system of claim 12, further comprising a second shaft fixed in the second body of water; a plurality of second flotation devices floating on the second body of water and connected together to surround the second shaft; a plurality of solar energy panels mounted on the second flotation devices at an angle relative to the horizon; and a second motor attached to at least one of the second flotation devices to rotate the second flotation devices about the second shaft.
 14. The solar energy system of claim 11, wherein the flotation devices are hexagonal.
 15. The solar energy system of claim 11, further comprising a controller for controlling the motor to rotate the flotation devices to track the sun.
 16. The solar energy system of claim 15, wherein the controller is configured to control the motor to rotate the flotation devices approximately 360° in 24 hours.
 17. The solar energy system of claim 11, further comprising a mechanism for adjusting the angle at which the solar panels are mounted on the flotation devices.
 18. The solar energy system of claim 11, further comprising bearings located between the shaft and the flotation devices.
 19. The solar energy system of claim 11, wherein the body of water comprises capacity for storing surplus water.
 20. A solar energy system comprising: first and second bodies of water, the second body of water being located at a higher elevation than the first body of water; at least one flotation device floating on at least one of the bodies of water; a plurality of solar panels mounted at an angle on the flotation device; a mechanism for rotating the flotation device to track the sun; a pump electrically coupled to the solar panels and configured to pump water from the first body of water to the second body of water; and a turbine positioned between the first and second bodies of water to extract energy from the water flowing from the second body of water to the first body of water. 